Most telephone users are familiar with what is referred to in the art as the line or mounting cord which extends the telephone circuits from a connecting block, either floor or wall mounted, to a telephone set. The telephone set consists of the housing, and the handset which is connected to the housing by a rectractile cord. Such line and retractile cords may be termed modular telephone cords.
There has been a significant effort to reduce the cost of these modular telephone cords. However, cost reduction cannot be accomplished at the expense any of the physical, mechanical or electrical requirements set forth for such cordage. One area in which cost reduction can be obtained is by providing a less expensive insulating material for the conductors of the modular telephone cords. Typically, the modular telephone cords have tinned tinsel conductors, individually insulated with a polymeric material such as Dupont's Hytrel 7246 and then jacketed with a PVC resin composition. Jacketing materials for telephone cordage have been discussed, for example, in U.S. Pat. No. 4,346,145.
The development of suitable compositions for the insulating material is complicated by the demanding requirements which telephone cordage must meet. Often, seemingly subtle differences in compositions can make the difference between meeting and not meeting certain requirements or the differnece in commercial acceptance and not.